Answer:
b. $250
Explanation:
In the given case, the marginal cost of firm is $250 per unit.
This marginal cost is constant. When the marginal cost is constant, it reflects the average variable cost.
average variable cost is also $250 per unit.
A firm shuts down when price is less than the average variable cost.
The price can go as lows as $250 per unit before the firm decides to shut down.
If price goes below the $250 per unit then firm will definitely shut down.